Technical Abstract: Mature dairy cattle were sampled over a two-year period (2001 - 2002) on six farms in New Mexico and Texas. Fecal samples were collected via rectal palpation, cultured for Salmonella, and one isolate from each positive sample serotyped. Three isolates of each serotype, with the exception of Salmonella Newport (n = 12), were examined for antimicrobial susceptibility using the broth micro-dilution technique. Twenty-two different serotypes were identified from a total of 393 Salmonella isolates. Montevideo was the predominant serotype (27%) followed by Mbandaka (15%), Senftenberg (11.4%), Newport (6.4%), Anatum (4.8%) and Give (4.8%). Salmonella Typhimurium and Dublin, two frequently reported serotypes, accounted for only 1% of the observed serotypes in this study. Sixty-four percent of the serotypes were susceptible to all of the antimicrobials, 14% were resistant to a single antibiotic, and 22% were multi-resistant (2 to 11 types of resistance). All isolates tested were susceptible to amikacin, apramycin, imipenem, ceftriaxone, nalidixic acid, and ciprofloxacin. The most frequent types of resistance were to sulfamethoxazole, tetracycline, streptomycin, kanamycin, chloramphenicol, and ampicillin (ranging from 8.9 to 22.4%). Serotypes demonstrating multiple resistance included Dublin and Give (resistant to 3 or more antibiotics), Typhimurium (resistant to 5 antibiotics) and Newport (4 and 2 isolates resistant to 6 and 9 antibiotics, respectively). Class 1 integrons were present in only three isolates, two Salmonella Dublin and one Salmonella Newport. The most prevalent resistance patterns observed in this study were for antimicrobial agents commonly used in cattle, while all Salmonella isolates were susceptible to ceftriaxone and ciprofloxacin, antibiotics used in human medicine.